Gated paper snubber

ABSTRACT

Apparatus to separate individual sheets fed from the top of the stack having a snubber-type stripper arranged to coact with a biased gate to buckle sheets of a first beam strength passing therethrough and to permit sheets of a greater beam strength to pass through the biased gate.

United States Patent George E. Fackler Inventor Loulsville, Ky. Appl. No. 838,780 Filed July 3, 1969 Patented July 13, 1971 Assignee Xerox Corporation Rochester, NY.

GATED PAPER SNUBBER 9 Claims, 6 Drawing Figs.

U.S. C1. 271/18, 271/36, 271/61 Int. Cl. B65h 3/00, B65h 3/16 Fieldolselrch 27l/18,22, 36, 61

n/mu Primary Examiner-Richard E. Aegerter Assistant Examiner-Douglas D. Watts Attorneys- Paul M. Enlow, Norman E. Schrader, James J.

Ralabate, Ronald Zibelli and Thomas .1. Wall ABSTRACT-z Apparatus to separate individual sheets fed from the top of the stack having a snubber-type stripper arranged to coact with a biased gate to buckle sheets of a first beam strength passing therethrough and to permit sheets of a greater beam strength to pass through the biased gate.

PATENTED JUL 1 3 I97! SHEET 1 OF 5 INVENTOR. GEORGE E. FACKLER L/ A7 TORNEY PATENIEU JUL 1 3 I971 SHEET 2 BF 5 PATENTEUJUL13I97I 3,592,462

SHEET 3 [IF 5 GATED PAPER SNUIBBER This invention relates in general to a sheet-feeding mechanism, and, in particular, to a device for causing a single sheet to be separated and advanced from a stack.

More specifically, this invention relates to a sheet separator or stripper for separating and forwarding individual sheets of various thickness and stiffness for use in a sheet-feeding device of the type in which sheets of a stack or pile of sheets are fed from the top seriatim. It is well known that the separation and feeding of sheets seriatim from a stack or pile of sheets presents many problems due to difference in weight, stiffness and/or surface characteristics of the paper to be conveyed by the sheet-feeding mechanism. Furthermore, for a given type of sheet the characteristics of the sheet are effected by variations in humidity and electrostatic condition in the areas in which the sheets are to be stored and used.

It is, therefore, the primary object of this invention to improve sheet separators for use in sheet-feeding mechanisms whereby the topmost sheet in a stack is separated from the remaining sheets of a stack.

A further object of this invention is to improve sheet separators capable of separating individual sheets from a stack independently of the surface characteristics of said sheets.

A further object of this invention is to separate individual sheets from the top of a stack regardless of the stiffness of said sheets.

A still further object of this invention is to improve sheet separators adapted to separate individual sheets from a stack whereby sheets of varying thickness will be satisfactorily separated and forwarded under a wide variety of conditions.

It is yet another object of this invention to improve apparatus for forwarding individual sheets from a stack in which sheets of various thickness and stiffness are forwarded without adjustment of said sheet separator.

These and other objects of the present invention are attained by means of a snubber plate slidably mounted in support members being adapted to overlay, in contact, the top front corners of the top sheets in a stack, a pivotally mounted gate being adapted to pivot about the support member and arrange to contact at least a portion of the leading edge of the top sheet in the stack, and means to bias said gate in contact with the topmost sheet with sufficient pressure to cause a sheet of a predetermined flexibility to buckle or be snubbed as the sheet is forwarded from the top of the stack and for a more rigid sheet to open said gate.

For a better understanding of the invention as well as other objects and features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. 1 illustrates schematically an automatic xerographic reproducing apparatus having a sheet-feeding mechanism using a preferred embodiment of the sheet separator or stripper of the instant invention;

FIG. 2 is a side elevation of the paper tray, sheet stripper and associated elements of the paper feed system;

FIG. 3 is a partial top view of the paper tray including the sheet separator constructed in accordance with the instant invention;

FIG. 4 is a sectional view of the sheet separator rolls and the associated elements;

FIG. 5 is an enlarged perspective view of the right-hand sheet separator shown in the preferred embodiment of the instant invention;

FIG. 6 is an enlarged perspective of a sheet separator embodying the teachings of the instant invention.

As shown, the xerogrnphic apparatus comprises a xerographic plate including a photoconductive layer of lightreceiving surface on a conductive backing and formed in a shape of a drum, generally designated by the numeral 10, which is joumaled in the frame of the machine. The xerographic plate is rotated in the direction indicated by the arrow (FIG. 1) to cause the drum surface to pass sequentially a plurality of xerographic processing stations.

For the purpose of the present disclosure the several xerographic processing stations in the path of movement of the drum surface may be described functionally as follows:

a charging station, in which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

an exposure station, at which a light or radiation pattern of an original document to be reproduced is projected onto the drum surface to dissipate the charge on the drum in the exposed areas thereof to form what is herein referred to as a latent electrostatic image of the original document to be reproduced; developing station, at which a xerographic developing material having toner particles possessing an electrostatic charge opposite to the charge found on the latent image are cascaded over the upwardly moving drum surface whereby the toner particles adhere to the electrostatic latent image to form a xerographic powder image in the configuration of the original document to be reproduced;

a transfer station at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer material or final support surface; and,

a drum-cleaning station, at which the drum surface is first charged and then wiped with a doctor blade to remove the residual toner particles remaining thereon after image transfer, and at which the drum surface is exposed to an illuminescent panel to affect substantially complete discharge of any residual electrostatic charge remaining thereon.

. The charging station is preferably located in the position indicated by reference character A in FIG. 1. The charging arrangement consists of a corona charging device 13 which in cludes a corona discharge array of one or more corona discharge electrodes that extend transversely across the drum surface and are energized from a high potential source. The corona discharge electrode is substantially enclosed within a shielding member and is adapted to generate a charge within a confined area.

Next subsequent thereto in the path of motion of the xerographic drum is an exposure station B. An optical scanning or projecting system is provided to project a flowing light image onto the flat stationary copy board 14. Basically the optical scanning or projection assembly comprises the stationary copy board which consists of a transparent platen positioned on the exterior of the cabinet and which is adapted to support an original document to be reproduced, means to illuminate uniformly the original document and which is arranged in light-projecting relationship to the moving photoconductive surface of the drum. Uniform lighting is provided by a single aperture lamp LMP-l attached to carriage l5, and the carriage mounted for movement transverse to the plan of the copy board.

A folded optical system including an object mirror 16, a movable lens 17, and an image 18 is used to direct the light image of the original onto the drum surface in this preferred embodiment of this invention. The lens element is positioned beneath the copy board and is arranged for movement in the path transverse to the plan of the copy board and is adapted to move in timed relation to the movement of the light source whereby the subject image of the original document supported by the copy board is scanned in timed relation to the movement of the light-receiving surface of the xerographic drum to project a light image corresponding to the original document onto the surface of said drum.

Positioned adjacent to the exposure station is fadeout panel 19 which is arranged to expose the drum surface in the areas between latent electrostatic images found thereon so that these nonimaged areas are not developed as the drum moves through the subsequent developing station. The fadeout panel reduces the charge on the drum surface below the level required for development.

Next adjacent to the exposure station is a developing station C in which is positioned a developer apparatus which includes a casting or housing 28 having a lower sump portion capable of accumulating a quantity of developer material therein. A bucket-type conveyor 27 having a suitable driving means is used to carry the developer material from the sump portion of the developer housing to the upper part of said housing where it is cascaded over the upwardly moving drum surface by means of a hopper chute 29. As the developer material is cascaded over the drum, toner particles are pulled away from the carrier component of the developer material and deposited on the drum surface in relation to the charge pattern found thereon to form a xerographic powder image. The partially denuded carrier material passes from the drum surface back into the developer housing sump. Fresh toner powder is supplied to the developer material in proportion to the amount of toner deposited on the drum surface by means of dispensing apparatus, generally designated 21.

Positioned next and adjacent to the developing station is the image transfer station D which includes sheet feeding and re gistering device 22 adapted to feed individual sheets of paper successively to the xerographic drum in coordination with the presentation of the developed image on the drum surface at this particular station. The transfer of the xerographic powder image from the drum surface to the final support material is effected by means of a corona generating device 24 that is located at or immediately after the point of contact between the sheet transfer material and the rotating drum surface. The corona transfer device is substantially similar to the corona discharge device employed at charging station A. in operation, the electrostatic field created by the corona discharge device is effective to tack the transfer material electrostatically to the drum surface whereby the transfer material moves synchronously with the drum while in contact therewith. Simultaneously with the tacking action, the electrostatic field is effective to attract the toner particles comprising the xerographic powder image from the drum surface and force the particles to adhere electrostatically to the surface of the transfer material.

Subsequent to the transfer station is positioned a plurality of mechanical stripper fingers 25 positioned to come into contact with the lower leading edge of the support material and being adapted to strip the leading edge of the material from the drum surface. The stripper fingers are shaped to direct the sheet material towards stationary vacuum transport 26. The sheet is held in contact with the bottom surface of the vacuum transport by means of vacuum ports positioned therein. The support material, a portion of which is electrostatically adhered to the drum surface is moved along the vacuum transport towards fuser assembly as the drum rotates in the direction indicated.

The image-bearing support material is moved along stationary vacuum transport 26 into the nip between upper fuser roll 31 and lower fuser roll 32. The rolls of fuser 30 coact to deliver pressure-driving force to a sheet of support material therebetween. A radiant source of energy 33 extending transverse to the lower roll transfers heat energy to the surface of the lower roll and the energy is brought into thermal contact with the image-bearing support material as the lower roll is rotated in the direction indicated. Image fixing is accom plished by a combination of pressure and heat energy transferred to the powder image as it is forwarded through the fuser 30. The fixed copy is transported through a circular paper path to a secondary feed tray 35 or the sheets are discharged V from the apparatus into catch tray 36 at a suitable point for collection. Movable guide and drive roll assembly 37 is pivotally mounted in the xerographic apparatus and is programmed by the machine logic system to be positioned in accordance with the mode of operation selected. At the same time the secondary feed tray is conditioned to accept sim plexed sheets from guide assembly 37.

The final processing station in the xerographic machine is the drum-cleaning station E having positioned therein preclean device 39; a drum-cleaning device, generally referred to as 40, adapted to remove residual toner from the drum surface by means of doctor blade 41; and an erase panel 42 adapted to expose the xerographic drum with sutficient energy to cause dissipation of any residual charge remaining on the drum surface.

Removal of residual powder from the drum surface is accomplished by means of doctor blade 4311 mounted transverse to the drum and arranged to be maintained in intimate contact across the photoconductive surface thereon. Residual toner removed by the blade falls into a trough area behind the blade and the residual toner is carried away from the drum area by means of auger 42. The residual toner returns to the developer housing 20 by means of a toner conveyor system (not shown) where it is used to recharge the developer system.

A single drive means is provided to drive the drum, movable lens, sheet feed mechanism, and fuser rolls at predetermined speeds in relation to each other and to also effect operation of the developer conveyor system and other operating systems.

It is believed that the foregoing description is sufficient for the purposes of this application to show the general operation of a xerographic reproducing apparatus using a sheet registration device constructed in accordance with this invention.

The sheet-feeding mechanism is positioned adjacent to the transfer station of the xerographic apparatus and is adapted for seriatim feeding of cut sheets of final support material, such as paper or the like, into contact with the drum surface so that the developed image thereon can be transferred to the final support material. The sheet-feeding mechanism consists of two paper feed trays 34 and 35 for holding a supply of cut sheets of final support material, separation rollers 63 separating a single sheet of support material from the individual trays and forwarding said sheet to a sheet-registering device 22, and drive means 50 for driving the separation rolls. Sheets of material fed into sheet-registering device are directed into a movable gate adapted to register and ali n the sheets and to forward them to xerographic transfer static D in timed relation with the xerographic image on the drum. The sheet of support material is advanced into the transfer station adjacent to the corona transfer device whereat the powder image previously formed on the drum surface is transfer it! from the drum to the support material. The sheet is then forwarded to a pressure heat fuser for image fixing. The fused copy, leaving the fuser is advanced by means of a set of delivery rolls which are arranged to either forward the individual sheets to collection trays 36 or into upper feed tray 35.

The two-tray arrangement gives a wide flexibility of usage to the xerographic reproducing apparatus. For example, duplex imaging of a single sheet of copy material can be accomplished by feeding sheets from the lower feed trays through the xerographic transfer and fusing station back to the upper feed tray. The simplexed sheets are collected in the upper tray until such time as a second original document is placed on copy board 14 and the sheets then programmed to be fed once again through the transfer station where the reverse side of the sheet is xerographically imaged. The reproducing apparatus is also capable of producing business instruments having more than just a single order. it is often desirable to make extra copies to be used for bookkeeping purposes, such as tabulations or business instruments. However, these other orders generally differ from the original order in color, size, and material. To achieve such multiple order production in the present reproducing apparatus, copy sheets of the second order placed in the remaining tray. With the reproducing apparatus of the kind described, the operator selects the number of sheets of the first order to be reproduced. These first order sheets are fed from a first feed tray. Upon completion of the first order run, the number of copies of the second or higher order are selected and the sheets fed from the second sheet feed trays. As can be seen, it is necessary to be able to feed automatically sheets of varying characteristics from the individual paper trays without having to adjust or replace the sheet-separatin g apparatus associated therewith.

, Basically, the individual sheet feed trays 34 and 35 (FIG. 1 l are of identical construction and include a platform or support member 62 upon which is slidably mounted right-hand and left-hand guide members. Because the guide members are formed complementary to each other, it is believed necessary to describe only one of the guides in detail for the purpose of this disclosure.

As shown in FIGS. 2 and 3, left-hand guide, generally designated 70, comprises a horizontal flange portion 71 and upright margin guides 72 and 73 and the vertical sheet guide arranged perpendicular to horizontal flange 71. Aperture 74 is machined in the guide member and provides an opening through which friction drag 75 can communicate with a stack being supported in the paper feed tray. Friction drag pads 75, having a plurality of bearing points 79 thereon, are affixed to leaf spring 80 by means of rivets 81 (FIG. 2). The leafspring is mounted on two embossed pads 82 on vertical sheet guide 72 and affixed thereto by means of studs 83 provided. As shown in FIG. 3, the drag pads are biased by the spring inwardly towards the center of the feed trays so that the bearing surfaces on the drag pad extend beyond the vertical side flanges when the spring is in the nonworking or unflexed condition.

The rightand left-hand guide members are adjustably mounted on the platform by conventional means in order to accommodate stacks of various size materials therebetween.

I In operation, a stack of sheets to be fed to the xerographic apparatus is positioned with the trailing edge of said sheet in contact with the vertical trailing edge guides 73. The leftand right-hand guide members 70 are moved and adjusted inwardly until the vertical sheet guides 72 contact the side margins of the stack thus positioning drag pads 75 in friction con tact with said stack.

In order to feed sheets of final support material one at a time from either of the paper trays, into the sheet-registering device 22 there is provided a paper-feeding means comprising intermittently driven rollers 63 fixedly mounted upon shaft 64 journaled in bearings 65 mounted in arm 66. The arm is adapted to swing about the axis of shaft 67 to place the rollers in contact with the top of the stack. The means for driving rollers 63 comprises a pulley 126 secured to a conventional slip clutch 51, and a pulley 52. The pulleys are mounted on shafts 64 and 67, respectively, and operatively connected together by means of timing belt 53. The slip clutch 51 permits the rollers to be rotated either by the timing belt 53 or by frictional contact with the sheet of transfer material as it is pulled forward by feed rollers positioned in the sheet-registering device 22.

Shaft 67 is journaled by means of a bearing 54 in backplate 9 of the machine frame and by a bearing 55 in arm 66. The shaft is normally biased to the left, as seen in FIG. 4, by means of spring 59 interposed between snap ring 56 fixed to the shaft and shaft encircling washer 55 butting against plate 9. As shaft 67 is forced to the left, the notched end of said shaft is forced into the aperture in the end of shaft 57 to engage the drive pin secured therein. Shaft 57 is journaled for rotation in bearing 84 mounted in sleeve 85 and the sleeve, in turn mounted in machine frame 8. A washer 87 rides in sleeve 85 against the machine frame to prevent outward axial movement of the shaft. Driving power to the rollers is provided by drive means 50 (FIG. 1) acting through shaft 57.

To adjust the pressure of rollers 63 on the stack material being supported in the feed trays, arm 66 is fixed to one end of a hollow arm shaft 86 and the opposite end of the am shaft being notched to engage locating pin 89 secured to the counter bore end of sleeve 85 journaled in machine frame 8. The roller pressure on the stack of paper in the paper tray due to the forces of gravity is sufficient to maintain the sheet of paper and rollers in friction driving contact when the two are in operative relation with each other.

In feeding sheets from the individual stacks, the topmost sheet in the stack is advanced forward. that is away from the vertical trailing edge guide 73 (FIG. 3) by the rotating feed rollers. The feed rollers act upon the topmost sheet to slide said sheet forward over the secondmost sheet in the stack. The movement of the topmost sheet therefore tends to advance the second sheet, the amount of movement depending on the surface characteristics of the sheets. In order to insure separation of only the topmost sheet from the stack, there is provided at opposite corners of the stack, gated snubbers, generally, designated 90, which are adapted to supply a restraining force to the topmost sheet as well as the leading edge of the uppermost sheets in the stack. The gated snubbers 90 like the edge guides are formed complementary to each other and it is believed necessary to describe in detail only one of these units for purposes of this disclosure. 7

The gated snubber 90 shown inFlG. 5 includes stop gate 91 which is mounted pivotably in slidable support member 92 so that the gate swings downwardly about pivot pin 93 retained in support 92. Also securely mounted in slidable support 92 by means of screws 94 is a snubber or snap-type separator 95. As shown in FIG. 3, slidable member 92 has a female T slot machined therein adapted to mate with T-shaped guide member 96 securely affixed to mounting posts 97 by means of studs 99. Mounting post 97 is secured to the vertical edge guide 72 and acts to secure and position the T-shaped guide 96 so that mating slidable member 92 moves parallel to the side edge margin of stack 100 (FIG. 4).

The gate is normally biased to a closed position against snubber by means of a torsion spring 101 wound upon pivot pin 93 and operatively connected to the U-shaped hinge portion 98 of the gate. In the biased or normally closed position, the working face of the gate, numerically referred to as 103, is supported in a vertical position substantially parallel to the leading edge of the stack and in contact with the front edge of snubber 95. The snubber or separator arm is adapted to overlay and contact the top corner edge of the topmost sheet in the stack. When the snubber is resting in contact with the topmost sheet in the stack the snubber and the gate cooperate to contain therebetween at least a portion of the leading edge of the topmost sheet as said sheet is forwarded from the stack.

Referring now to FIG. 2, gated snubber 90 is pivotally mounted in adjustable linkage 104 by means of pin 105. Linkage 104 is formed of two coacting arms shiftably connected by rivets 106 riding in slotted hole 107. The opposite end of the linkage is pivotally mounted about pin 108 staked to vertical guide 73 and held in spacial relation therewith by means of spacer 109 (FIG. 3). Also pivotally mounted upon staked pin 108 is counterweight 110. The counterweight is operatively connected to linkage by means of thumbscrew 111 riding in arcuate slotted hole 112. An embossed or weighted section 113 on the counterweight is offset sufficiently to cause the center of gravity of the counterweight to be located some distance from pivot point 108 and creates a mo ent about pin 108 tending to rotate the counterweight in a counterclockwise direction. When thumbscrew 111 is tightened the counterweight and movable linkage assembly 104 cooperate to move gated snubber assembly 90 downwardly in a vertical direction along the guide rails. The amount of pressure exerted by the snubber 95 upon the topmost sheet on the stack can be adjusted by repositioning the offset weighted counterbalance 110. That is, by loosening thumbscrew 111 and moving the weighted portion 113 about pin 108 the moment is increased or decreased thus changing the amount of pressure exerted by the snubber 95 on the topmost sheet in the stack.

In operation, the feed rolls forward the topmost sheet on the stack towards the sheet-registering device 22 (FIG. 1). When the topmost sheet is of light bond paper, such as letter paper, and the sheet is fed forward by the feed rollers, the leading edge of the paper strikes the working face 103 of gate 91. Because insufficient clearance is provided between the top of the gate and the lower surface of the snubber, the forward motion of the sheet is arrested. Sufficient biasing pressure is provided to hold the gate closed against the leading edge of the topmost sheet so that further forward movement of the light sheet causes the sheet to be buckled or snapped from under the snubber asthe sheet is forced from beneath the snubber. .The rear edge of the snubber forms an acute angle with the leading edge of the stack, tapering rearwardly towards the side margin of the stack so that the snubber plate has a wcdgelike shape. The forward edge of the topmost sheet is caused to buckle or snap over the wedgelike separator or snubber. As the sheet clears the snubber, the entire gated snubber assembly 90 is caused by the counterweight arrangement to move down into operative engagement with the next sheet on the stack.

It has been found that when the corners of a heavier sheet. such as card stock or the like, are forced to be buckled under a conventional snubber, the heavier material is damaged or torn. in the instant invention, heavier, or more rigid sheets forwarded into contact with the working surface of the pivoted gate 91 overcome the biasing pressure on the gate and swing the gate downwardly thereby permitting the sheet to be forwarded under rather than being buckled by snubber 95. Stiff sheets of material, because oftheir natural characteristics, can be individually separated and forwarded from the top of a stack by means of the feed wheels acting in cooperation with friction drag pads acting on the side margins of said stack, The

stiff sheets are separated much in the same manner as one deals cards from a deck of cards; the fingers of the supporting hand acting much as the drag pads act on the side of the stack,

and the thumb of the dealing hand acting in the same manner as the feed wheels to slide the top card forward. The biasing pressure on the gate is set so that the rigidity of the individual sheets automatically control the action of the gate, Sheets of marginal rigidity fed from a stack will sometimes activate the gate while at other times be snapped from under the snubber. However, because the characteristic of the sheet determines whether the gate is opened no damaging effects can result. In fact, in some cases, one corner of the sheet will be buckled by the snubber while the other corner of the sheet opens the gate without any damage to the sheet or misfeeding thereof.

I As the stack is reduced or depleted, the feed rollers and the gated snubbers acting under the force of gravity continue to remain in contact with the topmost sheet in the depleted stack and hence no stack-leveling device, such as an elevator or the like, need be utilized with the apparatus of the present invention.

FIG. 6 shows another embodiment of the instant invention in which the gate 125 is mounted to swing in a horizontal direction about pin 123. The gate is biased by a torsion spring similar to the one previously described to bias the gate against the leading edge of the stack. Here again the biasing pressure is set so that the rigidity of the individual sheets forwarded from the top of the stack determine whether the gate will be actuated or not. The less rigid sheets contacting the working face 124 of gate 125 are caused to buckle under the wedgeshaped snubber 95 while the more rigid sheets have sufficient rigidity to force the gate open.

While this invention has been described herein with reference to the xerographic machine and a specific sheetfeeding mechanism, it is not confined to the details as set forth, since it is apparent that the sheet separator of the invention could be used in any other type of reproducing machine and in connection with other forms of sheet-feeding mechanisms. Therefore, this application is intended to cover such modifications or changes as may come with the purposes of the scope of the following claims.

What I claim is:

1. In a sheet-feeding device for feeding the topmost sheet from a stack, apparatus to separate individual sheets from the top ofsaid stack including a support member slidably mounted and being positioned adjacent to the front side edge of said stack,

a snubber plate securely mounted to said slidably mounted support member and being arranged to overlay and contact the top front corner of the topmost sheet in said stack.

a pivotally mounted gate arranged to contact at least a portion of the leading edge of the top sheet in said stack, biasing means to hold said gate in contact with the edge of said snubber plate overlaying the leading edge of the stack.

2. The apparatus of claim 1 wherein said gate is biased into contact with the snubber plate with sufficient force to hold said gate in contact with said snubber when a sheet of a predetermined rigidity is forwarded therethrough and to allow said gate to open when a sheet of greater rigidity is forwarded theretl'irough.

3. The apparatus of claim 2 wherein the edge of said snubber plate positioned furthest from the side margin of said stack is tapered rearwardly at an acute angle relative to the leading edge of said stack to cause sheets separated thereby to be buckled inwardly from the side margin of the stack.

42. The apparatus of claim 3 wherein said gate is arranged to pivot in a vertical plane.

5. The apparatus of claim 3 wherein said gate is arranged to pivot in a horizontal plane.

6. In a sheet-feeding apparatus of the type having means to forward the topmost sheet from a stack along a predetermined path oftravel, the improvement comprising a pair of vertical support members positioned adjacent to the side margin ofsaid stack in close proximity to the leading edge thereof,

slidable members mounted for movement in a vertical direction in said vertical support members,

snubber means securely fixed to said slidable members and being arranged to overlay and contact the forward corners of said stack in a plane substantially parallel to the topmost sheet in said stack,

a gate pivotally mounted in said support members being arranged to contact said snubber means and being arranged to swing out of predetermined path of travel of the topmost sheet,

means to maintain said snubber in pressure contact with the.

topmost sheet in said stack,

biasing means to hold said gate in contact with the edge of said snubber overlaying the leading edge of the stack with sufficient force to hold said gate in contact therewith when a sheet of predetermined rigidity is forwarded therethrough and to allow said gate to open when a sheet ofgreater rigidity is forwarded therethrough.

7. The apparatus of claim 6 wherein the edge of said snubber plate positioned furthest from the side margin of said stack is tapered rearwardly at an acute angle relative to the leading edge of said stack to cause sheets separated thereby to be buckled inwardly from the side margin of the stack.

8. The apparatus of claim 7 having friction pads positioned along the side margin of said stack, said pads being arranged to be biased into contact with the side margins of at least the topmost sheet in said stack.

9. The apparatus of claim 8 wherein further means are provided to adjust the contacting pressure exerted by said snubber on the topmost sheet in said stack. 

1. In a sheet-feeding device for feeding the topmost sheet from a stack, apparatus to separate individual sheets from the top of said stack including a support member slidably mounted and being positioned adjacent to the front side edge of said stack, a snubber plate securely mounted to said slidably mounted support member and being arranged to overlay and contact the top front corner of the topmost sheet in said stack, a pivotally mounted gate arranged to contact at least a portion of the leading edge of the top sheet in said stack, biasing means to hold said gate in contact with the edge of said snubber plate overlaying the leading edge of the stack.
 2. The apparatus of claim 1 wherein said gate is biased into contact with the snubber plate with sufficient force to hold said gate in contact with said snubber when a sheet of a predetermined rigidity is forwarded therethrough and to allow said gate to open when a sheet of greater rigidity is forwarded therethrough.
 3. The apparatus of claim 2 wherein the edge of said snubber plate positioned furthest from the side margin of said stack is tapered rearwardly at an acute angle relative to the leading edge of said stack to cause sheets separated thereby to be buckled inwardly from the side margin of the stack.
 4. The apparatus of claim 3 wherein said gate is arranged to pivot in a vertical plane.
 5. The apparatus of claim 3 wherein said gate is arranged to pivot in a horizontal plane.
 6. In a sheet-feeding apparatus of the type having means to forward the topmost sheet from a stack along a predetermined path of travel, the improvement comprising a pair of vertical support members positioned adjacent to the side margin of said stack in close proximity to the leading edge thereof, slidable members mounted for movement in a vertical direction in said vertical support members, snubber means securely fixed to said slidable members and being arranged to overlay and contact the forward corners of said stack in a plane substantially parallel to the topmost sheet in said stack, a gate pivotally mounted in said support members being arranged to contact said snubber means and being arranged to swing out of predetermIned path of travel of the topmost sheet, means to maintain said snubber in pressure contact with the topmost sheet in said stack, biasing means to hold said gate in contact with the edge of said snubber overlaying the leading edge of the stack with sufficient force to hold said gate in contact therewith when a sheet of predetermined rigidity is forwarded therethrough and to allow said gate to open when a sheet of greater rigidity is forwarded therethrough.
 7. The apparatus of claim 6 wherein the edge of said snubber plate positioned furthest from the side margin of said stack is tapered rearwardly at an acute angle relative to the leading edge of said stack to cause sheets separated thereby to be buckled inwardly from the side margin of the stack.
 8. The apparatus of claim 7 having friction pads positioned along the side margin of said stack, said pads being arranged to be biased into contact with the side margins of at least the topmost sheet in said stack.
 9. The apparatus of claim 8 wherein further means are provided to adjust the contacting pressure exerted by said snubber on the topmost sheet in said stack. 